Nuclear energy and safety culture
Nuclear energy safety culture
Internationally the Atomic Energy Agency “ work with its member states and multiple partners world wide to promote safe, secure and peaceful operation of nuclear technologies. Some scientists say that the 2011 Japanese nuclear accidents have revealed that nuclear industry lacks sufficient over sight leading to renewed calls to redefine the mandate of IAEA so that it can better police nuclear power plants world wide. There are several problems with IAEA says Najmedin Meshkata of university of southern California.
It recommends safety standards, but member states are not required to comply, it promotes nuclear energy, but it is the sole global organization over seeing nuclear energy industry, yet it is also weighed down by checking compliance with nuclear non-proliferation treaty (NPT)
Many nations utilizing nuclear power have special institutions over seeing and regulating nuclear safety. Civilian nuclear safety in U.S. regulated by Nuclear Regulatory Commission (NRC). The safety of nuclear power plants and material controlled by U.S. Government for research, weapon production and those powering naval vessel is not governed by the NRC. In U.K. nuclear safety is regulated by office of nuclear regulation (ONR) and defense nuclear safety regulator (DNSR). The Australian radiation and nuclear safety agency (ARPANSA) is the federal government body that monitor and identifies solar radiation and nuclear radiation risks in Australia. It is the main body dealing with ionizing and non -ionizing radiation and publishes material regarding radiation projection.
Other agencies include
. Canadian nuclear safety association
. Radiological protection institute of Ireland
. Federal atomic energy agency in Russia.
.Kemfysische Dienst (NL)
. Pakistan nuclear regularity authority
. Bunde Samt for Strahlenschutz (DE)
. Atomic energy regulatory board (AERB) in India
Nuclear power plant
Nuclear power plants are some of most sophisticated and complex energy systems ever designed. Any complex system, no matter how well it is designed and engineered cannot be deemed failure proof Stephanie Cooke has reported.
The reactors themselves were enormous complex machines with an in calculable of things that could go wrong. When it is happened at Three Mile Island in 1979 another fault line in the nuclear world was exposed. One mal function led to another and series of others until the core reactor it self began to melt and even the world’s most highly trained nuclear engineers did not know how to respond. The accident revealed serious deficiencies in a system that was meant to protect public health and safety.
A fundamental issue related to complexity is that nuclear power systems have exceedingly long life times. The time frame involved from the start of construction of a commercial nuclear power state though to safe disposal of its last radio active waste may be 100 to 150 years.
Failure mode of nuclear power plants
There are concern that a combination of human and mechanical error at nuclear facility could result in significance harm to people and environment.
Operating nuclear reactors contain large amounts of radio-active fission products which, if dispersed, can pose a direct radiation hazard contaminate soil and vegetation, and be ingested by humans and animals. Human exposure at high enough level can cause both short term illness and death and long term death by cancer and other diseases.
Nuclear reactors can fail in a variety of ways. Should the instability of nuclear materials generate un expected behavior, it may result in un controlled power excursion. Normally the cooling system in a reactor is designed to be able to handle the excess heat this causes. However , should the reactor also experience a loss of coolant accident then the fuel may meet or cause the vessel it is contained in to over heat and melt. This event is called nuclear melt down.
After shutting down for some time the reactor still needs external energy to power its cooling systems. Normally this energy is provided by power grid that the plant is connected or by emergency diesel generators. Failure to provide power for cooling systems as happened in Fukushima can cause serious incidents.
Because the heat generated can be tremendous immense pressure can build up in the reactor vessel, resulting in steam explosion, which happened at Chernobyl. However the reactor design used at Chernobyl was unique in many ways. For example it had a large positive void coefficient meaning a cooling failure caused reactor to power rapidly escalate. Typical reactor design have negative void coefficient a passively safe design. However this design may not protect from melt down if cooling system is damaged.
More importantly though the Chernobyl plant leaked a containment structure. Western reactors have this structure, which acts to contain radiation in the event of a failure. Containment structure are by design, some of strongest structure built by mankind. However during serious incidents engineers may need to vent the containment intentionally as other wise it would crack due to excess of pressure .
Vulnerability of nuclear plants attack
Nuclear power plants are generally considered hard targets. In U.S. plants are surrounded by double row of tall fences which electronically monitored. The plant grounds are patrolled by a sizable force of armed guards. The NRCs design basis threat criteria for plant is a secret and so what size attacking force the plants are able to protect against is unknown.
However to scram (make emergency shut down) plant takes fewer than 5 seconds which unimpeded restart takes hours, severely hampering a terrorist force in a goal to release radioactivity.
The most important barrier against release of radioactivity in the event of an aircraft strike on a nuclear power plant is containment and its missile shield. Current NRC chair man Dale Klein has said “ nuclear power plants inherently robust structures that our studies show provide adequate protection in hypothetical attack. The NRC has also taken actions that require nuclear power plant operators to be able to manage large fires or explosions- no matter what has caused them.
In addition supporters point large studies carried out by the U.S. Electric power research institute that tested robustness of both reactor and waste fuel storage and found they should be able to sustain a terrorist attack comparable to the September 11 terrorist attack in U.S. spent fuel is usually housed inside plants “ protection zone “ or spent fuel shipping cask, stealing it for use dirty bomb is extremely difficult. Exposure to the intense radiation would almost certainly quickly incapacitated or kill any one who attempts to do so.
In September 2010, analysis of the stuxnet computer worm suggested that it was designed to sabotage a nuclear power plant. Such cyber attack would by pass the physical safe guards in place and so exploit demonstrates an important vulnerability.
Plant location
In many countries nuclear power plants are often located on the coast, in order to provide a ready source of cooling water for essential service water system. As a consequence the design needs to take risk of flooding and tsunami into account.
Failure to calculate the risk of flooding correctly leads to level 2 event on international nuclear event on the international nuclear event scale during 1999 Blayais nuclear power plant flood, while flooding caused by 2011 Tohoku earth quake and tsunami lead to the Fukushima Daaichi nuclear accidents.
The design of plants located in seismically active zones to be taken into account. Japan , India china and U.S. are among countries to have plants in earth quake prone regions. Damage caused to Japan Kashiwazaki- Kariwa nuclear power plant during 2007 Chuetsu offshore earthquake underlined concerns expressed by experts in Japan prior to Fukushima accidents, who have warned of domino -effect nuclear power plant earth quake disaster.
Nuclear safety system
The primary objective of nuclear safety systems as defined by nuclear regulatory commission are to shut down reactor, maintain it in shut down condition, and prevent release of radio active materials during events and accidents. These objective are accomplished using a variety of equipment, which part of different systems, of which each perform specific functions.
Hazards of nuclear material
Nuclear material may be hazardous if not properly handled or disposed of . Even when properly contained fission by products which are no longer useful to generate radioactive waste which must be properly disposed of. Spent nuclear fuel that is recently removed from nuclear reactor will generate large amounts of decay heat which will require pumped water cooling for an year or more to prevent over heating. In addition material exposed to neutron radiation-present in nuclear reactors may become radioactive on its own right, or become contaminated with nuclear waste. Additionally toxic or dangerous chemicals may be used as a part of plant operation which need be properly handled and disposed off.
New nuclear technologies
The next nuclear power plants to be built will likely be generation 111 or 111+ design and few of such are already in operation in Japan. Generation iv reactors would have greater improvements in safety. These designs are expected to be passively safe or nearly so, perhaps even inherently safe.
Some improvements made are having three sets of diesel generators and associated emergency core cooling systems rather than just one pair, having quench tanks (large cooled tanks) above the core that open into to automatically, having double containment ( one containment building inside another ) etc.
However safety risks may be the greatest when nuclear systems are newest, and operators have less experience with them. Nuclear engineer David Loch Baum explained that almost all serious nuclear accidents occurred with what was at the time the most recent technology. He argues that “ the problem with new reactors and accident is two fold. Scenarios arise that are impossible to plan for simulations, and hence human mistakes. As one director of U.S. RESEARCH laboratory put it “ fabrication, construction ,operation and maintenance of new reactors will face a steep learning curve. Advanced technologies will have a heightened a risk of accidents and mistakes. The technology is proven but people or not.
safety culture and human errors
one relatively prevalent notion in discussions of nuclear safety is that the safety culture. The international nuclear safety is that of safety advisory group defines term “ as personnel dedication accountability of all individuals engaged in any activity which has bearing on the safety of nuclear power plants. The goal is design systems that use human capabilities in appropriate ways, that protect systems from human frailties, and that protect human from hazardous associated with system.
At same time there is some evidence that operational practices are not easy to change. Operators almost never follow instruction and written procedures exactly and “ violation of rules appear to be quite rational, given the actual work load and timing constraints under which the operator must do their job” many attempts to improve nuclear culture “ were compensated by people adopting to change in an unpredicted way.
An assessment conducted by commissariat Energy Atomique (CEA) in France concluded that no amount of technical innovation can eliminate risk of human induced errors associated with operation of nuclear power plants. Two types of mistakes were deemed most serious ; errors committed during field operators, such as maintenance and testing that can cause an accident and human errors made during small accidents that cascade to complete failure.
According to Mycle Schneider, reactors safety depends above all on a “ culture of security, including the quality of maintenance and training, the complete of the operator and work force and the rigor of regulating over sight. So better designed new reactor is not always safe one and older reactors are not necessary dangerous than new one. The 1978 Three Mile Island accident in U.S. occurred in a reactor that had started operation only three months earlier and Chernobyl disaster occurred only two years of operation. A serious loss of coolant occurred at French Civaux-1 reactor in 1998 less than five months after start up.
Experts say that the “ largest single internal factor determining the safety of a plant is the culture of security of regulators, operators and work force- and it is essential to create such a culture.
Core damage risk
The AP 1000 has maximum core damage frequency of 5.09X 10-7 per plant per year. The evolutionary power reactor (EPR) has a maximum core damage frequency 4x 10-7 per plant for year. General electric has recalculated maximum core damage frequency for year per plant for its power plant design.
BWR/4------ 1x10-5
BWR/6-------1x10-6
ABWR-------2x10-7
ESBWR------3X10-8
HEALTH IMPACTS
In spite of accidents studies have shown the nuclear deaths are mostly in uranium mining and that nuclear energy has generated for fewer deaths than the high pollution levels that result from the use of conventional fossil fuels.
The speed of nuclear construction program in China has raised safety concerns. The challenge for government and nuclear companies is to “ keep an eye on growing army of contracts and sub contractors who may be tempted to cut corners. China is advised to maintain nuclear safe guards in business culture where quality and safety are some times sacrificed in favor of cost cutting, profits and corruption. China asked for international assistance in training more nuclear power plant inspectors.
Internationally the Atomic Energy Agency “ work with its member states and multiple partners world wide to promote safe, secure and peaceful operation of nuclear technologies. Some scientists say that the 2011 Japanese nuclear accidents have revealed that nuclear industry lacks sufficient over sight leading to renewed calls to redefine the mandate of IAEA so that it can better police nuclear power plants world wide. There are several problems with IAEA says Najmedin Meshkata of university of southern California.
It recommends safety standards, but member states are not required to comply, it promotes nuclear energy, but it is the sole global organization over seeing nuclear energy industry, yet it is also weighed down by checking compliance with nuclear non-proliferation treaty (NPT)
Many nations utilizing nuclear power have special institutions over seeing and regulating nuclear safety. Civilian nuclear safety in U.S. regulated by Nuclear Regulatory Commission (NRC). The safety of nuclear power plants and material controlled by U.S. Government for research, weapon production and those powering naval vessel is not governed by the NRC. In U.K. nuclear safety is regulated by office of nuclear regulation (ONR) and defense nuclear safety regulator (DNSR). The Australian radiation and nuclear safety agency (ARPANSA) is the federal government body that monitor and identifies solar radiation and nuclear radiation risks in Australia. It is the main body dealing with ionizing and non -ionizing radiation and publishes material regarding radiation projection.
Other agencies include
. Canadian nuclear safety association
. Radiological protection institute of Ireland
. Federal atomic energy agency in Russia.
.Kemfysische Dienst (NL)
. Pakistan nuclear regularity authority
. Bunde Samt for Strahlenschutz (DE)
. Atomic energy regulatory board (AERB) in India
Nuclear power plant
Nuclear power plants are some of most sophisticated and complex energy systems ever designed. Any complex system, no matter how well it is designed and engineered cannot be deemed failure proof Stephanie Cooke has reported.
The reactors themselves were enormous complex machines with an in calculable of things that could go wrong. When it is happened at Three Mile Island in 1979 another fault line in the nuclear world was exposed. One mal function led to another and series of others until the core reactor it self began to melt and even the world’s most highly trained nuclear engineers did not know how to respond. The accident revealed serious deficiencies in a system that was meant to protect public health and safety.
A fundamental issue related to complexity is that nuclear power systems have exceedingly long life times. The time frame involved from the start of construction of a commercial nuclear power state though to safe disposal of its last radio active waste may be 100 to 150 years.
Failure mode of nuclear power plants
There are concern that a combination of human and mechanical error at nuclear facility could result in significance harm to people and environment.
Operating nuclear reactors contain large amounts of radio-active fission products which, if dispersed, can pose a direct radiation hazard contaminate soil and vegetation, and be ingested by humans and animals. Human exposure at high enough level can cause both short term illness and death and long term death by cancer and other diseases.
Nuclear reactors can fail in a variety of ways. Should the instability of nuclear materials generate un expected behavior, it may result in un controlled power excursion. Normally the cooling system in a reactor is designed to be able to handle the excess heat this causes. However , should the reactor also experience a loss of coolant accident then the fuel may meet or cause the vessel it is contained in to over heat and melt. This event is called nuclear melt down.
After shutting down for some time the reactor still needs external energy to power its cooling systems. Normally this energy is provided by power grid that the plant is connected or by emergency diesel generators. Failure to provide power for cooling systems as happened in Fukushima can cause serious incidents.
Because the heat generated can be tremendous immense pressure can build up in the reactor vessel, resulting in steam explosion, which happened at Chernobyl. However the reactor design used at Chernobyl was unique in many ways. For example it had a large positive void coefficient meaning a cooling failure caused reactor to power rapidly escalate. Typical reactor design have negative void coefficient a passively safe design. However this design may not protect from melt down if cooling system is damaged.
More importantly though the Chernobyl plant leaked a containment structure. Western reactors have this structure, which acts to contain radiation in the event of a failure. Containment structure are by design, some of strongest structure built by mankind. However during serious incidents engineers may need to vent the containment intentionally as other wise it would crack due to excess of pressure .
Vulnerability of nuclear plants attack
Nuclear power plants are generally considered hard targets. In U.S. plants are surrounded by double row of tall fences which electronically monitored. The plant grounds are patrolled by a sizable force of armed guards. The NRCs design basis threat criteria for plant is a secret and so what size attacking force the plants are able to protect against is unknown.
However to scram (make emergency shut down) plant takes fewer than 5 seconds which unimpeded restart takes hours, severely hampering a terrorist force in a goal to release radioactivity.
The most important barrier against release of radioactivity in the event of an aircraft strike on a nuclear power plant is containment and its missile shield. Current NRC chair man Dale Klein has said “ nuclear power plants inherently robust structures that our studies show provide adequate protection in hypothetical attack. The NRC has also taken actions that require nuclear power plant operators to be able to manage large fires or explosions- no matter what has caused them.
In addition supporters point large studies carried out by the U.S. Electric power research institute that tested robustness of both reactor and waste fuel storage and found they should be able to sustain a terrorist attack comparable to the September 11 terrorist attack in U.S. spent fuel is usually housed inside plants “ protection zone “ or spent fuel shipping cask, stealing it for use dirty bomb is extremely difficult. Exposure to the intense radiation would almost certainly quickly incapacitated or kill any one who attempts to do so.
In September 2010, analysis of the stuxnet computer worm suggested that it was designed to sabotage a nuclear power plant. Such cyber attack would by pass the physical safe guards in place and so exploit demonstrates an important vulnerability.
Plant location
In many countries nuclear power plants are often located on the coast, in order to provide a ready source of cooling water for essential service water system. As a consequence the design needs to take risk of flooding and tsunami into account.
Failure to calculate the risk of flooding correctly leads to level 2 event on international nuclear event on the international nuclear event scale during 1999 Blayais nuclear power plant flood, while flooding caused by 2011 Tohoku earth quake and tsunami lead to the Fukushima Daaichi nuclear accidents.
The design of plants located in seismically active zones to be taken into account. Japan , India china and U.S. are among countries to have plants in earth quake prone regions. Damage caused to Japan Kashiwazaki- Kariwa nuclear power plant during 2007 Chuetsu offshore earthquake underlined concerns expressed by experts in Japan prior to Fukushima accidents, who have warned of domino -effect nuclear power plant earth quake disaster.
Nuclear safety system
The primary objective of nuclear safety systems as defined by nuclear regulatory commission are to shut down reactor, maintain it in shut down condition, and prevent release of radio active materials during events and accidents. These objective are accomplished using a variety of equipment, which part of different systems, of which each perform specific functions.
Hazards of nuclear material
Nuclear material may be hazardous if not properly handled or disposed of . Even when properly contained fission by products which are no longer useful to generate radioactive waste which must be properly disposed of. Spent nuclear fuel that is recently removed from nuclear reactor will generate large amounts of decay heat which will require pumped water cooling for an year or more to prevent over heating. In addition material exposed to neutron radiation-present in nuclear reactors may become radioactive on its own right, or become contaminated with nuclear waste. Additionally toxic or dangerous chemicals may be used as a part of plant operation which need be properly handled and disposed off.
New nuclear technologies
The next nuclear power plants to be built will likely be generation 111 or 111+ design and few of such are already in operation in Japan. Generation iv reactors would have greater improvements in safety. These designs are expected to be passively safe or nearly so, perhaps even inherently safe.
Some improvements made are having three sets of diesel generators and associated emergency core cooling systems rather than just one pair, having quench tanks (large cooled tanks) above the core that open into to automatically, having double containment ( one containment building inside another ) etc.
However safety risks may be the greatest when nuclear systems are newest, and operators have less experience with them. Nuclear engineer David Loch Baum explained that almost all serious nuclear accidents occurred with what was at the time the most recent technology. He argues that “ the problem with new reactors and accident is two fold. Scenarios arise that are impossible to plan for simulations, and hence human mistakes. As one director of U.S. RESEARCH laboratory put it “ fabrication, construction ,operation and maintenance of new reactors will face a steep learning curve. Advanced technologies will have a heightened a risk of accidents and mistakes. The technology is proven but people or not.
safety culture and human errors
one relatively prevalent notion in discussions of nuclear safety is that the safety culture. The international nuclear safety is that of safety advisory group defines term “ as personnel dedication accountability of all individuals engaged in any activity which has bearing on the safety of nuclear power plants. The goal is design systems that use human capabilities in appropriate ways, that protect systems from human frailties, and that protect human from hazardous associated with system.
At same time there is some evidence that operational practices are not easy to change. Operators almost never follow instruction and written procedures exactly and “ violation of rules appear to be quite rational, given the actual work load and timing constraints under which the operator must do their job” many attempts to improve nuclear culture “ were compensated by people adopting to change in an unpredicted way.
An assessment conducted by commissariat Energy Atomique (CEA) in France concluded that no amount of technical innovation can eliminate risk of human induced errors associated with operation of nuclear power plants. Two types of mistakes were deemed most serious ; errors committed during field operators, such as maintenance and testing that can cause an accident and human errors made during small accidents that cascade to complete failure.
According to Mycle Schneider, reactors safety depends above all on a “ culture of security, including the quality of maintenance and training, the complete of the operator and work force and the rigor of regulating over sight. So better designed new reactor is not always safe one and older reactors are not necessary dangerous than new one. The 1978 Three Mile Island accident in U.S. occurred in a reactor that had started operation only three months earlier and Chernobyl disaster occurred only two years of operation. A serious loss of coolant occurred at French Civaux-1 reactor in 1998 less than five months after start up.
Experts say that the “ largest single internal factor determining the safety of a plant is the culture of security of regulators, operators and work force- and it is essential to create such a culture.
Core damage risk
The AP 1000 has maximum core damage frequency of 5.09X 10-7 per plant per year. The evolutionary power reactor (EPR) has a maximum core damage frequency 4x 10-7 per plant for year. General electric has recalculated maximum core damage frequency for year per plant for its power plant design.
BWR/4------ 1x10-5
BWR/6-------1x10-6
ABWR-------2x10-7
ESBWR------3X10-8
HEALTH IMPACTS
In spite of accidents studies have shown the nuclear deaths are mostly in uranium mining and that nuclear energy has generated for fewer deaths than the high pollution levels that result from the use of conventional fossil fuels.
The speed of nuclear construction program in China has raised safety concerns. The challenge for government and nuclear companies is to “ keep an eye on growing army of contracts and sub contractors who may be tempted to cut corners. China is advised to maintain nuclear safe guards in business culture where quality and safety are some times sacrificed in favor of cost cutting, profits and corruption. China asked for international assistance in training more nuclear power plant inspectors.
posted by P M Babu Rao @ 7:38 PM
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what happen my readers vanished. i have email address have you posted my blog to them .pl help me .
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